Gas hydrate formations (clathrate formations) are terrestrial or marine formations containing gas hydrates. Gas hydrates are solids formed from gases (e.g., methane) and water under certain conditions of pressure and temperature. At low temperatures and high pressures the gases are enclosed in clathrate cages formed by water molecules. These conditions occur, e.g., in marine sediments in the ocean and in sediments of permafrost regions. There is an interest for several reasons in releasing the gases from gas hydrate formations. On the one hand, a large part of the world's hydrocarbon reserves are assumed to be bound in the form of gas hydrates in the sediments. Their release would open up a significant source of raw material. On the other hand, gas hydrate formations overlie large deposits of natural gas, e.g., in Siberia. An extraction of gas hydrates would facilitate the extraction of natural gas.
It is known that gaseous components can be released from gas hydrate formations by local elevations of temperature. A temperature elevation disturbs the equilibrium state of the hydrates in such a manner that the three-dimensional network of water cages releases the gases and the sediment remains with the water as a spongy matrix. Attempts to elevate the temperature by introducing water vapor or hot water in bores in sediments with gas hydrates are known (see, e.g., WO 99/19283, JP 09158662). However, these processes have proven to be ineffective and energy-intensive. Sediment layers with gas hydrates have a low permeability, so that the introduction of hot media is only possible with a high expenditure of energy.
Furthermore, US 2004/0060438 and DE 198 49 337 teach disturbing the thermodynamic equilibrium in gas hydrate formations by introducing liquid carbon dioxide or methanol and releasing gaseous components from the gas hydrate as a consequence thereof. However, this chemical treatment of gas hydrates is limited to local effects in the vicinity of a borehole and is furthermore characterized by an unfavorable energy balance. In addition, laboratory experiments show that an exchange of hydrate-bound methane with CO2 takes place only proportionately and therefore the complete methane gas cannot be extracted from the hydrates. The same applies to the extraction of methane hydrate with compressed air that is described, e.g., in WO 00/47832.
U.S. Pat. No. 6,148,911 teaches effecting the desired elevation of temperature by electrical heating. This technology has several disadvantages. In the first place, the course of the process is technically very complicated and energetically ineffective. Another disadvantage consists in a limitation to a narrow extraction plane on which a heating procedure can be carried out. Thus, a systematic extraction of gas hydrates in a geological formation is only possible with a high expenditure of time and energy.
Furthermore, the conventional release of gases from gas hydrate formations is associated with the following problems. The utilization of gas hydrates as a raw material source can be critical if the greenhouse gas CH4 is inadvertently released in large amounts during the extraction or if CO2 is released during the combustion of methane. Moreover, there can be a danger of a destabilization of geological formations resulting in significant risks to the environment, particularly in the case of the extraction of gas hydrates on continental shelves.
Studies for designing catalytic materials for a partial oxidation of methane are known (see, e.g., J. Schicks et al. in “Catalysis Today”, vol. 81, 2003, pp. 287-296; J. Schicks et al. in paper No. 348a, AICheE Annual Meeting, 2001, Reno, Nev.; G. Veser et al. in “Catalysis Today”, vol. 61, 2000, pp. 55-64; U. Friedle et al. in “Chemical Engineering Science”, vol. 54, 1999, pp. 1325-1352; U. Friedle et al. in D. Hänicke (editor), “Synthesis Gas Chemistry”, DGKM, Hamburg, 2000, p. 53 ff.). These studies were laboratory experiments with short reaction times.